The present invention relates to a fluid heater for use with heating solvents and flammable fluids. More particularly, the present invention relates to such a fluid heater having an embedded and hermetically sealed electrical junction box.
In the semiconductor chip fabrication process, it is well known that there is a need for cleaning processes to remove unwanted residues from the surface of a substrate (i.e. wafer). These cleaning processes are performed after fabrication operations such as plasma etching or chemical mechanical polishing (CMP). Some of these cleaning processes include the steps of dipping a semiconductor substrate into a chemical solution, rinsing the semiconductor substrate with deionized water, and then drying the semiconductor substrate. One way the semiconductor industry is using to accelerate the drying time is by rotating the wafer and displacing the deionized water with heated isopropyl alcohol which then evaporates more rapidly than the deionized water.
There also exist other processes, where it is advantageous to apply heated solvents, or other flammable fluids, to the wafer surfaces. It has been found that heating these solvents and closely controlling their temperature can improve yields, increase throughput and better control the desired wafer processing.
Heating solvents and flammable fluids present an increased risk of fire or explosion. Existing fluid heaters have designs that do not effectively reduce this risk. Such existing fluid heaters place the process fluid tube in direct contact with the heat source, where heat is transferred via conduction. The fluid tube isolates the fluid from direct contact with the heat source, but the electrical components of the fluid heater are left exposed to potential fumes in the environment or exposure to spills caused by a leak in the tubing or from a loose fitting.
Prior art heaters are generally not acceptable due to the risk of ignition by a malfunctioning electrical circuit and because most heaters are not designed in a manner that prevents solvent fumes or spills from having direct contact with the heating element or from entering the heater's electrical components. The separation of the fumes from the electrical components is critical for safety because fires can be started when these fumes are in direct contact with electrical components or areas in which a spark or electrical arc can occur.
Accordingly there is a need for an improved solvent heater that is safe, reliable and accurate—having a reduced risk of fire or explosion. The present invention fulfills these needs and provides other related advantages.